Table of Contents
Leaf may be defined as a flattened lateral out growth developing at the nodes of the stem and or its branches in acropetal succession. They are borne exogenously and bear buds in their axil.
Morphologically as well as anatomically, leaf is the most variable plant organ. Plants show many types of leaves which have different origin and functions. All types of leaves appearing on plant The phyllome. termed collectively as are phyllomes may be classified into following types. these are the Cotyledonary leaves., Cataphylls., Hypsophylls or bract leaves.,Floral leaves.,Sporophylls.,Foliage leaves.
- What is Cotyledonary leaves?
embryonic or seed leaves which appear as the first pair of leaves during gernmination. They provide nourishment to the young seedling.
- What is Cataphylls?
These are the scale leaves that appear on buds and underground stems. They are non-photosynthetic. Cataphylls protect the youno buds but in some plants these leaves also store food material (e.g., onion).
- What is Hypsophylls or bract leaves?
These leaves occur at the base of a flower or an inflorescence. These are mainly protective in function.
- What is Floral leaves?
Sepals, petals or perianth of flower are considered to be modified leaves.Sepals, which are usually green, are protective in function and the petals being coloured attract insects for pollination.
- What is Sporophylls?
These leaves are reproductive in function and bear spores. This term is also used for stamens and carpels of flower (micro-sporophylls and megasporophylls, respectively) which are considered to be modified leaves.
- What is Foliage leaves?
Green leaves of the plants are called foliage leaves. These are the principal photosynthetic organs. In the following pages the structure of the foliage leaves of angiosperms is described. A typical angiospermic leat consists of three parts, viz., leaf base, petiole and lamina.etc.
so well let’s know what is leaf base and what are the types of basic base types in angiospermic flower.
Leaf Base (Hypopodium)
The basal part of the leaf attached to the stem or branches is known as leaf base. Some types of bases found in angiosperms are mentioned below.
Pulvinus.,Sheathing.,Auriculate or semiamplexicaul.,Amplexicaul.,Decurrent.
- What is Pulvinus?.
This type of leaf base is swollen It forms a weak type of attachment. Tamarind, pea, gram, gold-mohur, mango, banyan,Mimosa, etc., have pulvinus leaf base.
- What is Sheathing?.
In monocotyledons the leaf base is expanded into a broad sheath that encloses the stem for some distance above the node. Examples include sugarcane, grasses, maize, banana, etc., (the pseudostem in banana is formed by sheathing leaf bases).
- What is Auriculate or semiamplexicaul?.
In this type the leaf base partially encloses the stem. Examples are prickly poppy Calotropis procera (madar), etc.
- What is Amplexicaul?.
The leaf base completely encloses the stem. Examples: Sonchus,Polygonum, etc.
- What is Decurrent?.
In some plants the leaf base becomes expanded like a wing and extends down the stem so that the latter also seems to be winged. Examples Laggera pterodonta, Symphytum, etc,.
The leaf base in many plants is associated with one or two minute appendages called stipules. The stipules may be either attached to the leat base or are present on both the sides as lateral lateral sides as the outgrowths. Leaves with stipules are terned as stipulate (e.g., Rosa, Polygonum) and those without stipules are called exstipulate (e.g.. Ipomoea). In compound leaves tiny, inconspicuous stipule-like appendages occur at the hase of the leaflets. They are known as stipels and leaflets with stipels are called stipellate.
So, here we know what is stipules? and now you have to know, what are the types of stipules?
[I] Types of stipules
Stipules may be classified into following three types on the basis of duration for which they remain attached to the leaf base.
Caducous,Deciduous,Persistent,Free-lateral.Scaly,Adnate,Interpetiolar,Intrapetiolar,Ochreate,Foliaceous,Spinous,Tendrillar,Convolute or ventral.
- What is Caducous?.
These stipules fall off before the unfolding of leaf, e.g., Michelia champaca.
- What is Deciduous?
Such stipules fall off soon after the leaf unfolds, e.g., Cassia tora, Dillenia indica.
- What is Persistent?
These are permanent stipules which remain attached to the leaf for the whole of its life; e.g., Rose, Pea. On the basis of their structure and relation to the leaf, stipules may be of following types.
- What is Free-lateral?
The two stipules are borne on the two sides of leaf base e.g., Hibiscus (china rose).
- What is Scaly?
These are small dry scales, usually two in number, borne on two sides of the leaf base; e.g., Desmnodium, Spergula.
- What is Adnate?
In this type two lateral stipules grow adhering to the petiole up to a certain height thus making it somewhat winged; e.g.,rose.
- What is Interpetiolar?
In this type two stipules lie between the petioles of opposite or whorled leaves, e.g., Ixora, Mussaenda.
- What is Intrapetiolar?
These stipules are situated between the petiole and the axis; e.g Tabernaemontana.
- What is Ochreate?
Such stipules form a hollow tube around the internode of stem. It extends from the node up to a certain height, in front of the petiole; e.g., Polygonum.
- What is Foliaceous?
When the stipules are large and green leafy structures they are called foliaceous. They are usually two in number; e.g Lathyrus (sweet pea), Pisum (pea).
- What is Spinous?
Here stipules are modified into spines, usually one such stipule lies on each side of the leaf base: e.g Zizyphus,
Barleria prionitis, Acacia.
- What is Tendrillar?
These stipules are modified into tendrils. Usually one such stipule lies on each side of the petiole e.g., Smilax.
- What is Convolute or ventral?
In Ficus, Magnolia Ricinus, etc., stipules occur on the ventral side of the petiole. The margins of these stipules meet one another and serve as bud scales is protect young buds,
Petiole or the leaf-stalk is a small, stem-like structure which connects the lamina with the branch. The petiole has two main functions:
(1) conduction of food material between lamina and stem
(2) bringing the lamina to favourable position with respect to.light through its growth in length and bending or twisting. Leaves with petiole are known as petiolate and those without petiole are called sessile. In sessile leaves lamina is directly attached to the stem.
it’s ok so you know probably what is petiole? (mesopodium) and what are the function of mesopodium petiole? and know you have to know, what are the types of petiole?
The shape and form of petioles vary in different species. Some common types of petiole are given below
- What is Filiform?
These are and slender long petioles, e.g., Ricinus.
- What is Striate?
This type of petiole is marked with longitudinal lines; e.g, Ficus.
- What is Phyllode?
This is a petiole modified into a flattened leaf-like structure; e.g., Australian acacia (Acacia auriculaeformis). In Parkinsonia, secondary rachis is inodified into a leaf-like structure and is also called phyllode.
- What is Tendrillar?
In some weak climbers the petiole gets modified into tendril and helps the plant in climbing; e.g., Clematis,
- What is Bulbous petiole?
In some aquatic plants the petiole becomes swollen and spongy, thereby helping the plant in floating on water surface; e.g., Eichhornia
- What is Winged?
Here the petiole becomes flattened and wing-like, resembling leaf lamina; e.g., Citrus (lemon, orange, etc.).
What is Lamina?
Lamina is the green expanded part of leaf. It is the most conspicuous and, in general, the most important part of a leaf. A thick midrib, extending from petiole to the tip of lamina, usually divides the lamina into two halves. The midrib gives out lateral branches, called primary -veins, which in turn divide repeatedly and form a network of veinlets throughout the lamina.
Lamina performs three vital functions, viz.photosynthesis, respiration and transpiration.
Here we know what is Venation? what are the main function of Venation? and what are the types of Venation? let’s see
What is Venation?
Leaves of angiosperms have a characteristic branched vascular system. It consists of one or more principal or main veins originating from the tip of the petiole and their several branches the veinlets. The arrangement of principal veins and veinlets in the lamina is termed as venation.
What are the types of venation?
The veins are chiefly made of vascular tissue. the xylem and phlocm. They nave two important functions:
(1) mechanical support to lamina and
(2) supply of water and minerals (absorbed by roots) to all cells of the leaf and transport of organic food synthesized by green cells of the leaf to all non-greeh cells of the plant.
There are following two main types of venation:
(1) Parallel venation and
(2) Reticulate venation
[I] what is Parallel venation
In this type veins run parallel to each other from base to the tip of the lamina. Veinlets connecting the adjacent longitudinal veins are inconspicuous. it is characteristic of monocotyledonous leavęs but a few dicotyledons (e.g.Calophyllum) also show as parallel venation.
- Parallel unicostate. In this type there is only one principal vein which gives off many lateral veins These run towards the margins or apex of laminain a more or less parallel manner; e.g canna, banana.
- Parallel multicostate. The leaf has man principal veins arising from the tip of the peti and these run upwards or outwards. It may be of following two types:
(a) Convergent type. Here several principal veins arise from the base of lamina and converge towards its apex; e.g.. grasses, wheat. bamboo.
(b) Divergent type. In this type principal veins arising from the tip of the petiole, diverge towards the margin of leaf blade in a more or less paran manner; e.g., fan palms.
[II] what is Reticulate venation
This is a pattern of venation in which the veinlets are repeatedly branched and form an irregularly distributed complex network. It is characteristic of dicotyledonous leaves. However, some monocotyledons (e.g., Smilax, Dioscorea and aroids) also show reticulate venation.
Depending upon the number of principal veins, reticulate venation may be divided into following two categories.
- what is Reticulate unicostate?
In this type, there is only one principal vein that gives off many lateral veins which run towards margin or apex of the leaf; e.g., mango, banyan, china rose.
- what is Reticulate multicostate?.
This is a type, where two or more principal veins arising from the tip of the petiole run upward. The two types of reticulate multicostate venation are
(a) Convergent type. Many principal veins arise from the tip of the petiole, spread upwards in a curved manner and
converge towards the apex of leaf blade; e.g., Cinnamomum, Zizyphus jujuba
(b) Divergent type. In this type many principal veins arise from the tip of the petiole and diverge from one another towards the margins of leaf blade; e.g., castor, cucumber.
- What is morphology of a plant?
- What do you mean by the morphology of leaves?
- What are the different types of leaves and shape of leaves ?
- What is wilting?
- What is the importance of leaf morphology in plants?
- Why are leaves green in Colour?
- What are the two main types of leaves?
- Why is the structure of a leaf important?
- What is the significance of leaf structure in photosynthesis?
- What are some environmental factors affect the rate of photosynthesis and how?